Data transfer systems with power management

ABSTRACT

A controller for transferring data between a host and a storage medium includes a data transfer unit and a control unit. The data transfer unit transfers data according to control commands from the host if the data transfer unit is enabled. The control unit coupled to the data transfer unit receives a status signal indicating whether the storage medium is coupled to a socket of the controller. The control unit provides interruption signals to the host. Power and a clock signal for the control unit are disabled if the status signal indicates that the storage medium is decoupled from the controller.

BACKGROUND

A storage medium such as a memory card or a flash media card is a datastorage device and can be used in electronic devices and systems,including digital cameras, mobile phones, laptop computers, mediaplayers, video game consoles, etc. The storage medium can bere-recordable, and can retain data without power. A card reader isattached to a host, e.g., a personal computer, and has a socket toconnect a storage medium. When a storage medium is coupled to thesocket, the card reader can transfer data between the host and thestorage medium.

FIG. 1 shows a conventional data transfer system 100. The data transfersystem 100 includes a host 102, a controller 104, and a storage medium108, e.g., a flash media card. The controller 104 includes a datatransfer unit 110, a control unit 112, a filter 124 and a socket 106. Adata path, including the data transfer unit 110 and the data lines 165and 152, is used to transfer data between the host 102 and the storagemedium 108. A control path, including the control unit 112, the filter124, and the control lines 164, is used to control the data transfer ofthe data transfer system 100.

The control unit 112 and the filter 124 monitor the status of thestorage medium 108, e.g., whether the storage medium 108 is coupled tothe socket 106. In operation, if the storage medium 108 is coupled tothe socket 106, the socket 106 generates a monitoring signal 150 to thefilter 124. The filter 124 removes noises of the monitoring signal 150and provides the status signal 154 to the control unit 112. The controlunit 112 further includes a card detection circuit 122 and aninterruption circuit 120. The card detection circuit 122 coupled to thefilter 124 receives the status signal 154 and enables the data transferunit 110 if the status signal 154 indicates that the storage medium 108is coupled to the socket 106. The interruption circuit 120 generates aninterruption signal 164 in response to the status signal 154. Theinterruption signal 164 is transferred to the host 102 according to astandard interface protocol, for example, Peripheral ComponentInterconnect-Express (PCIe), Universal Serial BUS (USB), Serial AdvancedTechnology Attachment II (SATA2), or Advanced Technology Attachment(ATA). Upon receiving the interruption signal 164, the host 102 readsthe status register of the interruption circuit 120 to obtain the statusinformation of the storage medium 108. If the storage medium 108 iscoupled to the socket 106, the host 102 can control the data transferunit 110 to exchange data with the storage medium 108.

However, when the storage medium 108 is decoupled from the socket 106,the control unit 112 keeps being powered on, such that the control unit112 can generate the interruption signal 164 once the storage medium 108is inserted again. As such, the power consumption of the data transfersystem 100 is relatively high.

SUMMARY

In one embodiment, a controller for transferring data between a host anda storage medium includes a data transfer unit and a control unit. Thedata transfer unit transfers data according to control commands from thehost if the data transfer unit is enabled. The control unit coupled tothe data transfer unit receives a status signal indicating whether thestorage medium is coupled to a socket of the controller. The controlunit provides interruption signals to the host. Power and a clock signalfor the control unit are cut off if the status signal indicates that thestorage medium is decoupled from the controller.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the claimed subject matterwill become apparent as the following detailed description proceeds, andupon reference to the drawings, wherein like numerals depict like parts,and in which:

FIG. 1 illustrates a block diagram of a conventional data transfersystem.

FIG. 2 illustrates a block diagram of a data transfer system, inaccordance with one embodiment of the present invention.

FIG. 3 illustrates another block diagram of a data transfer system, inaccordance with one embodiment of the present invention.

FIG. 4 illustrates another block diagram of a data transfer system, inaccordance with one embodiment of the present invention.

FIG. 5 is a flowchart of operations performed by a data transfer system,in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments of the presentinvention. While the invention will be described in conjunction withthese embodiments, it will be understood that they are not intended tolimit the invention to these embodiments. On the contrary, the inventionis intended to cover alternatives, modifications and equivalents, whichmay be included within the spirit and scope of the invention as definedby the appended claims.

Embodiments described herein may be discussed in the general context ofcomputer-executable instructions residing on some form ofcomputer-usable medium, such as program modules, executed by one or morecomputers or other devices. Generally, program modules include routines,programs, objects, components, data structures, etc., that performparticular tasks or implement particular abstract data types. Thefunctionality of the program modules may be combined or distributed asdesired in various embodiments.

Some portions of the detailed descriptions which follow are presented interms of procedures, logic blocks, processing and other symbolicrepresentations of operations on data bits within a computer memory.These descriptions and representations are the means used by thoseskilled in the data processing arts to most effectively convey thesubstance of their work to others skilled in the art. In the presentapplication, a procedure, logic block, process, or the like, isconceived to be a self-consistent sequence of steps or instructionsleading to a desired result. The steps are those requiring physicalmanipulations of physical quantities. Usually, although not necessarily,these quantities take the form of electrical or magnetic signals capableof being stored, transferred, combined, compared, and otherwisemanipulated in a computer system.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present application,discussions utilizing the terms such as “receiving,” “transferring,” orthe like, refer to the actions and processes of a computer system, orsimilar electronic computing device, that manipulates and transformsdata represented as physical (electronic) quantities within the computersystem's registers and memories into other data similarly represented asphysical quantities within the computer system memories or registers orother such information storage, transmission or display devices.

By way of example, and not limitation, computer-usable media maycomprise computer storage media and communication media. Computerstorage media includes volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information such as computer-readable instructions, data structures,program modules or other data. Computer storage media includes, but isnot limited to, random access memory (RAM), read only memory (ROM),electrically erasable programmable ROM (EEPROM), flash memory or othermemory technology, compact disk ROM (CD-ROM), digital versatile disks(DVDs) or other optical storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium that can be used to store the desired information.

Communication media can embody computer-readable instructions, datastructures, program modules or other data in a modulated data signalsuch as a carrier wave or other transport mechanism and includes anyinformation delivery media. The term “modulated data signal” means asignal that has one or more of its characteristics set or changed insuch a manner as to encode information in the signal. By way of example,and not limitation, communication media includes wired media such as awired network or direct-wired connection, and wireless media such asacoustic, radio frequency (RF), infrared and other wireless media.Combinations of any of the above should also be included within thescope of computer-readable media.

Furthermore, in the following detailed description of the presentinvention, numerous specific details are set forth in order to provide athorough understanding of the present invention. However, it will berecognized by one of ordinary skill in the art that the presentinvention may be practiced without these specific details. In otherinstances, well known methods, procedures, components, and circuits havenot been described in detail as not to unnecessarily obscure aspects ofthe present invention.

FIG. 2 illustrates a block diagram of a data transfer system 200, inaccordance with one embodiment of the present invention. In the exampleof FIG. 2, the data transfer system 200 includes a host 202, acontroller 204, and a storage medium 208. The storage medium 208 can be,but is not limited to, a card-shaped storage medium such as a flashmedia card or a memory card. The host 202 can be an electronic device orsystem, such as a computer, a personal digital assistance (PDA), amobile phone, or the like. The controller 204 coupled between the host202 and the storage medium 208 is configured to transfer data accordingto the control commands from the host 202, and to monitor the status ofthe storage medium 208, e.g., whether the storage medium 208 is coupledto the controller 204. In one embodiment, the controller 204 includes asocket 206, a filter 224, a control unit 212, and a data transfer unit210.

In one embodiment, the socket 206 coupled between the storage medium 208and the filter 224 can be coupled to various types of storage medium.For example, the socket 206 can be a TF (Trans-Flash) type to be coupledto a TF card, or a SD (Secure Digital) type to be coupled to a SD(Secure Digital) card. The socket 206 generates a monitoring signal 250indicating a status of the storage medium 208, e.g., whether the storagemedium 208 is coupled to or decoupled from the socket 206. For example,the monitoring signal 250 can be a one-bit digital signal having a firststate, e.g., digital one, and a second state, e.g., digital zero. By wayof example, when the monitoring signal 250 is digital one, it indicatesthat a storage medium is coupled to the socket 206. When the monitoringsignal 250 is digital zero, it indicates that the storage medium isdecoupled from the socket 206.

The filter 224 coupled to the socket 206 can be, but is not limited to,a Kalman filter, and is configured to receive the monitoring signal 250and to eliminate or reduce noises of the monitoring signal 250 togenerate a status signal 254. The status signal 254 is transferred toboth the control unit 212 and the host 202. In one embodiment, thestatus signal 254 is used by the control unit 212 to enable or disablethe data transfer unit 210, and is used by the host 202 to control powerdelivered to the controller 204.

The control unit 212 coupled to the filter 224 includes a card detectioncircuit 222 and an interruption circuit 220. The card detection circuit222 is configured to generate an enable signal 232 to enable or disablethe data transfer unit 210 according to the status signal 254. Morespecifically, if the status signal 254 indicates that a storage medium208 is coupled to the socket 206, the card detection circuit 222 enablesthe data transfer unit 210. Accordingly, the data transfer unit 210 cantransfer data if the host 202 generates control commands via a controlline 268 to request a data transfer. If, however, the status signal 254indicates that the storage medium 208 is decoupled from the socket 206,the card detection circuit 222 disables the data transfer unit 210.Thus, the data transfer unit 210 does not transfer data even if the host202 requests a data transfer.

The interruption circuit 220 is coupled to one or more functionalcomponents such as the card detection circuit 222 and the data transferunit 210. The interruption circuit 220 monitors statuses of thefunctional components and generates interruptions to the host 202according to the statuses. In one embodiment, the interruption circuit220 generates an interruption if an error occurs to a functionalcomponent. In another embodiment, the interruption circuit 220 generatesan interruption if a status of a functional component is changed. Uponreceiving the interruption, the host 202 checks the interruption circuit220, e.g., by reading interruption registers contained in theinterruption circuit 220, to further obtain information of thecorresponding functional component. In one embodiment, the carddetection circuit 222 generates an interruption signal indicating thatthe data transfer unit 210 is enabled. The interruption circuit 220receives the interruption signal from the card detection circuit 222,and generates an interruption signal 264 to the host 202, indicatingthat the data transfer unit 210 is ready for the data transfer.

The data transfer unit 210 coupled between the host 202 and the socket206 transfers data between the host 202 and the storage medium 208. Inone embodiment, when the data transfer unit 210 is enabled by the enablesignal 232, the data transfer unit 210 transfers data from the storagemedium 208 to the host 202 if the host 202 transmits a read command via268 to the data transfer unit 210, and transfers data from the host 202to the storage medium 208 if the host 202 transmits a write command vialine 268 to the data transfer unit 210.

In one embodiment, the host 202 provides power and a clock signal to thecontroller 204 and the storage medium 208 through the power and clocksignal lines 262. The host 202 further determines whether to provide thepower and the clock signal to a particular unit in the controller 204and generates a power/clock control signal 266 to control the deliveryof the power and the clock signal accordingly. In one embodiment, thecontroller 204 includes a power management unit 270 coupled to the host202. The power management unit 270 receives the power/clock controlsignal 266, and delivers the power and the clock signal to differentunits in the controller 204 accordingly.

In the example of FIG. 2, the power management unit 270 has lines 272for providing the power and the clock signal to the data transfer unit210 and the control unit 212, and has a line 274 for providing the powerto the filter 224. The filter 224 has its own clock signal inside, inone embodiment. Therefore, the control unit 212 and the filter 224 canhave different power and clock conditions according to the power/clockcontrol signal 266 from host 202. In an alternative embodiment, thepower management unit 270 is included in the host 202. The controller204 can have other configurations, and is not limited to the example ofFIG. 2.

Advantageously, the host 202 has a pin coupled to the filter 224, suchthat the status signal 254 can be directly transferred from the filter224 to the host 202. As such, information about the status of thestorage medium 208 can be forwarded to the host 202 without goingthrough the control unit 212. In one embodiment, if the status signal254 indicates that there is no storage medium coupled to the socket 206of the controller 204, the power management unit 270 provides power tothe filter 224 but disables (cuts off) the power and the clock signal tothe data transfer unit 210 and the control unit 212 according to thepower/clock control signal 266 from host 202. If the status signal 254indicates that a storage medium is coupled to the socket 206, the powermanagement unit 270 provides the power and the clock signal to the datatransfer unit 210 and the control unit 212, and keeps providing power tothe filter 224 according to the power/clock control signal 266. Asneither the power nor the clock signal is provided to the data transferunit 210 and the control unit 220 when the storage medium 208 isdecoupled from the socket 206, the power consumption of the datatransfer system 200 is reduced.

FIG. 3 illustrates an example of a block diagram of a data transfersystem 300, in accordance with one embodiment of the present invention.Elements labeled the same as in FIG. 2 have similar functions. FIG. 3 isdescribed in combination with FIG. 2. The data transfer system 300includes a host 202, a controller 204, and a storage medium 208, in oneembodiment.

In one embodiment, the host 202 includes a processor 301, a power source307, a clock generator 305, and an interface 303. The processor 301 canbe a central processing unit (CPU), a microprocessor, a digital signalprocessor, or any other such device that can read and executeprogramming instructions. The processor 301 can execute instructioncodes to generate control commands to the power source 307, the clockgenerator 305, and the controller 204. In operation, the processor 301controls the power source 307 and the clock generator 305 to deliverpower 361 and a clock signal 363 to the power management unit 270. Thepower management unit 270 provides the power 361 and the clock signal363 to different units in the controller 204 according to the controlsignal 266, as described in relation to FIG. 2.

Moreover, the processor 301 exchanges data and control information withthe controller 204 through the interface 303. The interface 303 servesas an I/O (input/output) interconnect between the processor 301 and thecontroller 204. In one embodiment, the processor 301 operates as amaster to start a data transfer. The processor 301 can send the controlinformation to the controller 204 via the interface 303. The controlinformation can enable a hand-shake between the processor 301 and thecontroller 204 before the data information is transferred. The controlinformation can define a characteristic of the data transfer, forexample, whether the data is written into the storage medium 208 or readfrom the storage medium 208. For example, the data information can betransferred from the processor 301 to the controller 204 in a writeoperation, and the data information can be transferred from thecontroller 204 to the processor 301 in a read operation. The controlinformation can also indicate a status of the data transfer, forexample, start/initiation of the data transfer or completion of the datatransfer.

In one embodiment, the interface 303 analyzes the informationtransferred from the processor 301 to determine if the processor 301transfers data information or control information. The interface 303 canselectively transfer the information through a data path 265 or acontrol path 268 depending on whether the processor 301 transfers thedata information or the control information. If the host transfers thedata information, the data can be sent to the controller 204 through thedata path 265. If the processor 301 transfers the control information,the control information can be sent to the controller 204 through thecontrol path 268. Moreover, the interface 303 can convert the datainformation from the controller 204 into data readable by the processor301 (computer-readable data) and transfer the data to the processor 301.

The interruption circuit 220 includes a generator 315 and a register317. The register 317 can store the information received from the carddetection circuit 222 and some other interruption information, e.g.,requesting for reading data or requesting for writing data. Uponreceiving the interruption information, the generator 315 generates theinterruption signal 264 which is read by the processor 301.

The data transfer unit 210 coupled between the interface 303 and thesocket 206 includes a host-side control circuit 309, a data buffer 311,and a device-side control circuit 313. The device-side control circuit313 coupled between the data buffer 311 and the socket 206 receives theenable signal 232 and operates as a switch to conduct or cut off thedata path 252 between the data buffer 311 and the storage medium 208according to the enable signal 232. For example, when the storage medium208 is coupled to the socket 206, the enable signal 232 enables thedevice-side control circuit 313 to conduct the data path 252. Thus, datainformation can be exchanged between the storage medium 208 and thebuffer 311. When the storage medium 208 is decoupled from the socket206, the enable signal 232 disables the device-side control circuit 313to cut off the data path 252.

The host-side control circuit 309 coupled between the data buffer 311and the interface 303 operates as a switch for controlling the host sideto transfer data information. In operation, when the host 202 receivesthe interruption signal 264 indicating that the card detection circuit222 enables the device-side control circuit 313, the host 202 generatescontrol commands to enable the host-side control circuit 309 via thecontrol path 268. Thus, the data path 265 between the data buffer 311and the interface 303 is conducted. When both the host-side controlcircuit 309 and the device-side control circuit 313 are enabled, thedata can be transferred between the host 202 and the storage medium 208via the data paths 265 and 252.

The data buffer 311 coupled between the host-side control circuit 309and the device-side control circuit 313 is configured to buffer the datainformation from the interface 303 and the storage medium 208. Forexample, when the host 202 writes data information to the storage medium208, the data buffer 311 buffers the data information from the interface303 and provides the data information to the storage medium 208.Similarly, when the host 202 reads data information to the storagemedium 208, the data buffer 311 can buffer the data information from thestorage medium 208 and provide the data information to the interface303.

FIG. 4 illustrates a block diagram of a data transfer system 400, inaccordance with one embodiment of the present invention. Elementslabeled the same as in FIG. 2 and FIG. 3 have similar functions. FIG. 4is described in combination with FIG. 2 and FIG. 3.

In the embodiment of FIG. 4, the filter 224 is further coupled to thepower management unit 270 via a signal line 466. The power managementunit 270 receives the status signal 254 via the line 466 and determineshow to deliver the power and the clock signal to different units in thecontroller 204 accordingly.

In one embodiment, when the system is initialized, the host 202 providesthe power via the line 361 and the clock signal via the line 363 to thepower management unit 270. The power management 270 transfers the powerand the clock signal through lines 272 to the data transfer unit 210 andthe control unit 212, and transfers the power through line 274 to thefilter 224. In one embodiment, when the system is initialized, the wholecontroller 204 is powered on. In operation, the filter 224 sends thestatus signal 254 to the host 202, the card detection circuit 222, andthe power management unit 270. Thus, the host 202, the card detectioncircuit 222, and the power management unit 270 obtain the statusinformation of the storage medium 208, e.g., whether the storage medium208 is coupled to the socket 206. If no storage medium is coupled to thesocket 206, the power of the filter 224 transferred via the line 274remains on, while the power and the clock signal of the data transferunit 210 and the control unit 212 via lines 272 are disabled (cut off)by the power management unit 270 according to the status signal 254 viathe line 466. If the storage medium 208 is coupled to the socket 206,the power management unit 270 keeps turning on the power at line 274 andthe power and the clock signal at the lines 272 according to the statussignal. That is, the power and the clock signal of the control unit 212and the data transfer unit 210 are both enabled. The card detectioncircuit 222 receives the status signal 254 and enables the device-sidecontrol circuit 313. Accordingly, the interruption circuit 220interrupts the processor 301 to inform that the device-side controlcircuit 313 is enabled. Thus, the processor 301 enables the host-sidecontrol circuit 309 if the processor 301 is ready to transfer data.

Advantageously, when the storage medium 208 is removed from the socket206, the control unit 212 and the data transfer unit 210 are both shutoff, which reduces the power consumption of the driving circuit 400.

FIG. 5 illustrates a flowchart 500 of operations performed by a datatransfer system, e.g., the data transfer system 200, 300 or 400, inaccordance with one embodiment of the present invention. Althoughspecific steps are disclosed in FIG. 5, such steps are examples. Thatis, the present invention is well suited to performing various othersteps or variations of the steps recited in FIG. 5.

In block 502, a status signal, e.g., the status signal 254, indicatingwhether a storage medium, e.g., the storage medium 208, is coupled to asocket of a controller, e.g., the controller 204, is transferred to ahost, e.g., the host 202.

In block 504, power and a clock signal to a control unit, e.g., thecontrol unit 212, of the controller are cut off if the status signalindicates that the storage medium is decoupled from the socket.

In block 506, the power and the clock signal to the control unit of thecontroller are turned on if the status signal indicates that the storagemedium is coupled to the socket.

In block 508, a data transfer unit, e.g. the data transfer unit 210, isenabled and disabled by the control unit according to the status signal.In one embodiment, the data transfer unit is enabled if the statussignal indicates that the storage medium is coupled to the socket and isdisabled if the status signal indicates that the storage medium isdecoupled from the socket.

In block 510, data is transferred according to control commands from thehost if the data transfer unit of the controller is enabled.

While the foregoing description and drawings represent embodiments ofthe present invention, it will be understood that various additions,modifications and substitutions may be made therein without departingfrom the spirit and scope of the principles of the present invention asdefined in the accompanying claims. One skilled in the art willappreciate that the invention may be used with many modifications ofform, structure, arrangement, proportions, materials, elements, andcomponents and otherwise, used in the practice of the invention, whichare particularly adapted to specific environments and operativerequirements without departing from the principles of the presentinvention. The presently disclosed embodiments are therefore to beconsidered in all respects as illustrative and not restrictive, thescope of the invention being indicated by the appended claims and theirlegal equivalents, and not limited to the foregoing description.

What is claimed is:
 1. A controller for transferring data between a hostand a storage medium, said controller comprising: a data transfer unittransferring said data according to control commands from said host ifsaid data transfer unit is enabled; and a control unit, coupled to saiddata transfer unit, that receives a status signal indicating whethersaid storage medium is coupled to a socket of said controller, thatcontrols said data transfer unit according to said status signal, andthat provides a plurality of interruption signals to said host, whereinpower and a clock signal for said control unit are cut off if saidstatus signal indicates that said storage medium is decoupled from saidsocket.
 2. The controller as claimed in claim 1, wherein said power andsaid clock signal for said control unit are turned on if said statussignal indicates that said storage medium is coupled to said socket. 3.The controller as claimed in claim 1, wherein said control unitcomprises a card detection circuit which receives said status signal,and enables and disables said data transfer unit according to saidstatus signal.
 4. The controller as claimed in claim 3, wherein saidcard detection circuit enables said data transfer unit if said statussignal indicates that said storage medium is coupled to said socket, andwherein said card detection circuit disables said data transfer unit ifsaid status signal indicates that said storage medium is decoupled fromsaid socket.
 5. The controller as claimed in claim 1, wherein said powerand said clock signal for said data transfer unit are turned on if saidstatus signal indicates that said storage medium is coupled to saidsocket, and wherein said power and said clock signal for said datatransfer unit are cut off if said status signal indicates that saidstorage medium is decoupled from said socket.
 6. The controller of claim1, further comprising: a filter, coupled to said socket, that generatessaid status signal provided to both said control unit and said host. 7.A data transfer system comprising: a host; a storage medium; acontroller coupled between said host and said storage medium andoperable for transferring data between said host and said storagemedium, said controller further comprising: a data transfer unittransferring data according to control commands from said host if saiddata transfer unit is enabled; a control unit, coupled to said datatransfer unit, that receives a status signal indicating whether saidstorage medium is coupled to a socket of said controller, that controlssaid data transfer unit according to said status signal, and thatprovides a plurality of interruption signals to said host, wherein powerand a clock signal for said control unit are cut off if said statussignal indicates that said storage medium is decoupled from said socket.8. The data transfer system as claimed in claim 7, wherein said powerand said clock signal for said control unit are turned on if said statussignal indicates that said storage medium is coupled to said socket. 9.The data transfer system as claimed in claim 7, wherein said controlunit enables said data transfer unit if said status signal indicatesthat said storage medium is coupled to said socket, and wherein saidcontrol unit disables said data transfer unit if said status signalindicates that said storage medium is decoupled from said socket. 10.The data transfer system as claimed in claim 7, wherein said power andsaid clock signal for said data transfer unit are turned on if saidstatus signal indicates that said storage medium is coupled to saidsocket, and said power and said clock signal for said data transfer unitare cut off if said status signal indicates that said storage medium isdecoupled from said socket.
 11. The data transfer system as claimed inclaim 7, wherein said host further comprises a pin, which is operablefor receiving said status signal from said filter.
 12. The data transfersystem as claimed in claim 7, wherein said storage medium comprises aflash media card.
 13. A method for transferring data information betweena host and a storage medium, said method comprising: transferring astatus signal indicating whether a storage medium is coupled to a socketof a controller to said host; cutting off power and a clock signal to acontrol unit of said controller if said status signal indicates thatsaid storage medium is decoupled from said socket; transferring saiddata according to control commands from said host if a data transferunit of said controller is enabled.
 14. The method as claimed in claim13, further comprising: turning on said power and said clock signal tosaid control unit of said controller if said status signal indicatesthat said storage medium is coupled to said socket.
 15. The method asclaimed in claim 13, further comprising: turning on said power and saidclock signal to said data transfer unit if said status signal indicatesthat said storage medium is coupled to said socket; and cutting off saidpower and said clock signal to said data transfer unit if said statussignal indicates that said storage medium is decoupled from said socket.16. The method as claimed in claim 13, further comprising: enabling anddisabling said data transfer unit by said control unit according to saidstatus signal.
 17. The method as claimed in claim 16, furthercomprising: enabling said data transfer unit if said status signalindicates that said storage medium is coupled to said socket, anddisabling said data transfer unit if said status signal indicates thatsaid storage medium is decoupled from said socket.